Method of tapering metallic rods and the like



IN VEN TOR ATTORNEY rlHMHMHH HHHH III! I!!! May 9, 1933. T. VARNEY METHOD OF TAPERING METALLIC RODS AND THE LIKE Filed April 30, 1930 i 5 rod and from 40 rod to stretch Patented May 9, 1933 7 UN ED-STATES PATENT OFFICE THEODORE VARNEY, OF NEW YORK, 'N. Y., ASSIGNOR TO ALUMINIUM LIMITED, OF

' TORONTO, ONTARIO, CANADA METHOD OF TAPERING- METALLIC RODS AND THE LIKE App1ication filed April 30,

This invention relates to a method of producing tapers on metallic rods and the like.

It is a prime aim of the present invention to provide a method whereby longer tapers 5 than were heretofore thought possible from a practical standpoint may be produced, and a method whereby tapers of any length may be more expeditiously and inexpensively formed than heretofore. 1 An important object is to provide a method whereby the article or rod, or the portion thereof to be tapered, will be reduced in strength proportionately from a given point and then subjected to longitudinal stretching 1 whereby it will be stretched in proportion to the strength, these operations resulting in the desired taper.

Another object is to provide for heating the rod or portion to be stretched, in order to proportionately reduce the strength thereof as mentioned above, through the use of a transformer in an electric circuit having the terminals of the secondary in conducting relation to the rod at the limits of the portion .2 to be tapered.

I A still. further object is to provide ventilat'ing means for accurately controlling the relative temperature of the different parts of the rod during the heating process, to pro- 'duce a more uniform taper upon the drawing thereof. Further, it is aimed to provide a method whereby the taper may be provided by reducing the strength of a portion of a rod between two clamps or the like engaging the a point midway of the clamps and progressively decreasing in degree of reduction toward the clamps, and in subsequently moving one or both of the clamps away from the other while attached to the the rod, which accordingly produces the taper.

' The method and the apparatus therefor are illustrated in the accompanying drawing, wherein:

Fig. 1-is aplan view of an apparatus con- 7 structed in accordance with my invention, showing the parts in the position assumed at the start of an operation and during the reduction of thestrength of the rod;

2 is a sectional view taken on the line 1930. Serial No. 448,717.

IIII of Fig. 1, also indicating in dotted lines the parts in position at the end of an operation; and

Fig. 8 is a cross section on the line III III of Fig. 1.

Referring specifically to the drawing, 10 designates a metallic rod which is to be formed into two rods each having a taper of any length desired. Such rod is usually round 11 cross section, but may be square or any other shape.

Secured rigidly to the rod 10 in spaced relation, and extending completely therearound, are ]8.WS or clamps 11 and 11a of any desired construction, to enable application and removal thereof.

Such clamps 11 are of electrical conducting material, and have the terminals of a secondary coil or winding 12 of a transformer 13 connected thereto. Said transformer has its primary coil or winding 14, through its leads 15, adapted for connection with any source of alternating electric current of suitable voltage and frequency.

1 have shown, as a preferred embodiment 75 of my invention, a base member B of nonconducting material as, for example, wood, having a longitudinal T-slot 16 therein for slidably mounting the clamp or jaw 11, as clearly shown in Fig. 3. The clamp 11a is fixedly secured to the base by means of bolts or screws 17.

For the purpose of translating the clamp 11 to taper-draw the rod 10, I have provided a connecting rod 18 suitably insulated from and secured to said clamp at one end, and having a piston 19 on its other end, said piston adapted for reciprocation in a cylinder 20 by the application of compressed air or other fluid thereto, as will be readily understood.

In practicing the invention, the parts are initially connected as in Fig. 1, and electric current is supplied to the primary winding ll and low voltage current of large volume or amperage-is induced through the secondary winding 12, flowing through the clamps 11 and 11a and the portion of the rod 10 located between them. By adjusting the amount of the current and the length of time it flows, the middle point of the rod between the jaws, which is indicated at a, will be raised to a temperature very much higher than that of the other parts of the rod or the surrounding medium, the temperature or degree of heating from the said point a progressively decreasing in opposite directions toward the clamps 11 and 11a. This results in correspondingly reducing the strength of the metal between said clamps, that is, the portion of rod between the clamps has maximum weakness at the point a and progressively increases instrength in opposite directions therefrom to said clamps.

The clamp 11a, as described, is preferably held stationary at this stage, while compressed air or other fluid is applied to the cylinder 20, thereb moving piston 19 and the clamp 11 to t e right to the position shown in the dotted lines of Fig. 2, and, as it is rigidly connected to the rod, stretching the portion of the rod 10 between such clamps into the shape also indicated in dotted lines in'Fig. 2, a shape including uniform oppositely tapered portions b which may be readily severed at their connecting apices. The tapered'portion b may be of any length desired, since the present invention overcomes those obstacles in previous methods permitting only short tapered portions to be formed.

Attention is called to the fact that the stretching of the rod does not have to immediately follow the heating and reducing of the strength thereof since the essential step is to reduce the strength as described. The

rod reduced in strength may even'be cooled before the stretching 'step is practiced.

Taking a specific example, suppose a rod of hard drawn aluminum were that represented at 10. Its ultimate strength would be approximately24,000 pounds per square inch. However, if the rod were annealed dead soft in a furnace, then allowed to cool, and tested, it would be found that the ultimate strength was reduced to about 12,000 .pounds per square inch. If, therefore, a rod 10 of hard drawn aluminum is engaged by clamps 11 and 11a, as illustrated, and the current is applied for a proper length of time, the center point a of the rod can be heated up to the full annealing temperature of the rod.

If the adjustment of the current and time is maintained correct, it will be possible to 55 cut oil the current, thereby at that instant leaving the temperature of the rod at the jaws or clamps 11 practically the same as that of the surroundin air, and leaving the tempera- .5 ture of the mi dle point of the rod at a very uch higher temperature, say, for example, ji QO degrees F. or more. This temperature of course be adjusted for any value desirdwithin the melting point of the material. 7" When the current is cut off and the rod fiuieid cooled,as by means of an air bla'st or water spray, or even if it were allowed to cool off itself in the air, the rod would, after it cooled off, be annealed at the center point and have progressively varying annealed conditions at other points from o posite sides of the. int a to'the 'aws. At e jaws, the rod won 3 remainhar drawnbe cause of the cooling effect of the jaws.

It has been found in'practice that themethod just described may be carried out with better results providing the air surround' the rod 10 is stationary while said rod is being heated by the electric currents.

The amount of energy which is developed by the current in the rod is the same at every point throughout its length btvveentlie ws when the current first begins'to new. The middle point between the ewe increases iiiore rapidly in temperaturetha'ii'the other successive points between the middle and thefjai'v's, for the reason that the heat which is 21am. oped by the current flows'away'thrd htlie wire or rod intothe heavy'and relativiifi cool jaws. As the temperature of the rod increases, the air immediately surrronii' ihgthe rod becomes heated andit rises, 'thereb'y displacing the cooler air and convection currents are set up which tend to cool thefrod.

If the rod were entirely enclosed in 'an'air chamber so that the air could not getawa from the rod, it would heat more rapidly and also the desired effect would be more readily obtained. However, if the central portionof the rod is positioned within a tightly enclosed chamber, and then each successive section of 00 the rod between the middle and the jawwei'e enclosed in a separate chamber, the ventilation of which was controlled, the relative telnperatures of the different parts of the 5 may be regulated accuratel To this end, I provide a ventilating or cool- 1ng regulating device consisting of a base member 21 adapted to be sitioned on-the base B, and having longitu inally extendingg spaced-apart side members 22 secured can a trally of the base member 21. The rod 10 is passed through the chamber 23 between the members 22, said chamber being divided into a series of smaller chambers 24 by means of vertical partitions 25, preferably formed of asbestos or other heat resisting material, the latter having central openings 26 therethrough to receive the rod 10.

As shown and as preferred, I haveprovided an unequal number of small-chambers 24 to uniformly control the heat of the rod 10 from its middle point a outwardly inboth directions to the clamps or jaws 11 and 11a, The chamber 24a is clcd "at'the-bottom for I26 the purpose of minimiiing the 'cdiivectibn iifirrents, tending to cool the rodthefmting thereof. The remaining chambeifs'fiire provided with openings 27 at the 'bo'twm. thereof for the purpose of intrdducing air around the remaining portion of the rod 10 during the heating process.

It will be noted that the openings 27 increase in size toward the jaws or clamps 11 and 11a to uniformly reduce heating of the rod from the high temperature at the point a outwardly in both directions to the cool sections of the rod contained in said clamps.

I claim:

1. Means for tapering a metallic body including spaced-apart clamp members, an interposed cooling regulating device for directing air currents at spaced intervals onto the body to effect a non-uniform cooling of the body, means for subjecting said body to an electric circuit, and means for moving a clamp member to efiect stretching of said body.

2. Means for tapering a metallic body including spaced-apart clamping members, an interposed cooling regulating device including a plurality of longitudinal spaced chambers in which the body is disposed for directing spaced air currents onto the body, means for subjecting said body to an electric circuit, and means for moving a clamp member to effect stretching of said body.

3. Means for tapering a metallic body including spaced-apart clamping members, an interposed cooling regulating device including a plurality of longitudinally spaced chambers in which the body is disposed, means for subjecting said body to an electric circuit, and means for moving a clamp member to effect stretching of said body, one of said chambers having a closed bottom and one of said chambers open at its bottom.

4. Means for tapering a metallic body including spaced-apart clamping members, an interposed cooling regulating device including a plurality of longitudinally spaced chambers in which the body is disposed, means for subjecting said body to an electric circuit, and means for moving a clamp member to efiect stretching of said body, said chambers having bottom openings of varying diameters to direct non-uniform currents onto the body.

5. The method of imparting taper to a metallic body consisting of reducing the body in strength by heating the body and then imparting a stretching tension to said body characterized in that 'the reduction in strength of the body is controlled by causing controlled air currents to be directed onto the body.

6. In the method of imparting taper to a metallic body consisting of reducing the body in strength by heating the body and then imparting a stretching tension to said body, the feature that in order to obtain a gradual taper in said body reduction in the strength of the body is controlled by establishing and subjecting the body to controlled air currents.

7 In the method as specified in claim 6, the feature that the air currents directed to difl'erent portions of said body are non-uniform.

In testimony THEODORE VARNEY. 

